Apparatus for applying pressure-sensitive adhesive to sheet material



Dec. 20, 1960 H c. PAULSEN 2,965,066

APPARATUS FOR APPLYING PRESSURE-SENSITIVE ADHESIVE TO SHEET MATERIAL Filed Nov. 21, 1958 4 Sheets-Sheet 1 INDICATOR /7[AT HEAT MOTOR lnven tar Hans C Paul'sen By his Attorney Dec. 20, 1960 H. c. PAULSEN APPARATUS FOR APPLYING PRESSURESENSITIVE ADHESIVE T0 SHEET MATERIAL 4 Sheets-Sheet 2 Filed Nov. 21, 1958 1960 H. c. PAULSEN ,965,

APPARATUS FOR AP ING ESSURE- SITIVE ADHESIVE SH MATERI Filed NOV. 21, 1958 4 Sheets-Sheet 3 1960 H. c. PAULSEN 2,965,066

APPARATUS FOR APPLYING PRESSURE-SENSITIVE ADHESIVE TO SHEET MATERIAL Filed Nov. 21, 1958 4 Sheets-Sheet 4 limited States Patqent APPARATUS FOR APPLYING PRESSURE-SENSI- TIV E ADHESIVE TO SHEET MATERIAL Hans C. Paulsen, Lexington, Mass., assignor to United Shoe Machinery Corporation, Flemington, N.J., a corporation of New Jersey Filed Nov. 21, 1958, Ser. No. 775,612

Claims. (Cl. 118-5) This invention relates to apparatus for applying to sheet material a thin layer of viscous, relatively heat-resistant pressure-sensitive adhesive and, as illustrated herein, is embodied in a machine for applying to a limited area of a price tag or other form of sheet material a suitable pressure sensitive adhesive coating for attachment to an article of merchandise. The illustrated apparatus is of the type disclosed in United States Letters Patent No. 2,878,777, granted March 24, 1959 upon application of the present inventor, the present application being a continuation in part of the application from which that patent matured.

Most pressure-sensitive adhesives are of organic nature and are, accordingly, easily decomposed and their adto spread into a uniformly thin coating upon sheet material by reason of its high viscosity and relative heat- -resistant nature, the viscosity remaining at about forty thousand centipoises at a critical temperature of 350 F. At this temperature the adhesive readily flows from a heating reservoir through a horizontal passageway, terminating in an upwardly directed outlet opening leading to the point of application on the sheet material, as set forth in United States Letters Patent No. 2,861,899, granted November 25, 1958 upon application of Edwin E. Sylvester and Sumner H. Peck. However, this temperature is critical not only because it is at the lower end of a range within which the adhesive flows readily but it is close to one in which undesirable decomposing effects take place in the adhesive, so that the adhesive may become discolored and lose at least some of its adhesive qualities if the temperature is maintained for an extended period. This is especially true unless extremely accurate control is maintained on the temperature of the reservoir and along any relatively narrow passageways connected with the outlet opening close to the point of application where the highest temperatures are required.

An object of the present invention is to provide an apparatus for applying to sheet material a layer of viscous pressure-sensitive adhesive, which is relatively heat resistant in that it softens and becomes sufiiciently fluid for application only at a temperature which is close to that at which decomposition of the adhesive occurs, the

while maintaining other essential safeguards in the control of the machine. In accordance with the purposes above outlined th apparatusof the invention has a heated supply reservoir formed with a laterally projecting base provided with .:i

several adjacent parallel passageways extending in a horiwith adhesive requiring heating to a critical temperature;

zontal plane from the reservoir into the projecting base portion, one of which passageways enters the reservoir and conducts adhesive into the base, another of which passageways has an electrical heating cartridge inserted for convenient replacement, an upper surface of the base having an outlet opening running from one end of the adhesive passageway and an elongated thermostat for regulating the temperature of the adhesive as it passes through the outlet opening in the base, which thermostat extends horizontally through the base directly above and crossing the adhesive conducting and heating cartridge passageways between the reservoir and the outlet opening. Preferably, there are two heating cartridges employed, the second one of which is inserted in a third passageway at the opposite side of the adhesive passageway from the first-mentioned heating cartridge receiving passageway. In the illustrated form of this feature an adhesive spreading motor driven roll is mounted in the outlet opening of the base, and a second elongated thermostat is arranged in parallel relation to the firstmentioned thermostat but is spaced further away from the outlet opening, the second thermostat being electrical ly connected in circuit with the motor for driving the roll to open the motor circuit whenever the temperature of the base drops below the critical temperature of the adhesive. In this way the danger of damaging the machine in an attempt to rotate the roll while gripped with con gealed adhesive is avoided and the necessity for utilizing an adhesive containing a solvent is avoided. Consequently, there is no necessity for providing special cooling and drying devices in the present apparatus, such as required in the prior art, the coated sheet material being ready for use immediately after application to the sheet material. Other features of the invention relate to improvements in compact construction and effective arrangement of the heating cartridges and thermostats in a manner to obtain closer control of the temperature than is possible with prior machines.

These and other features, as hereinafter described and claimed, will readily be apparent to those skilled in the art following the detailed specification and accompanying drawings, in which:

Fig. 1 is a plan view partly broken away and shown in section of a pressure sensitive adhesive processing and applying apparatus embodying the features of the present invention;

Fig. 2 is a view of a price tag composed of sheet material, such as fiber board, of which a limited area is covered with the pressure sensitive adhesive, so that the tag may be adapted for quick attachment to an article of merchandise;

Fig. 3 is an enlarged view in front elevation, partly broken away and in section, of the adhesive processing and applying apparatus, illustrated in Fig. 1 together with an adhesive supply container;

Fig. 4 is a sectional view on a reduced scale of the apparatus taken along the line IV-IV of Fig. 3;

Fig. 5 is an enlarged fragmentary sectional view taken along the line VV of Fig. 3; and

Fig. 6 is a wiring diagram of the apparatus.

The apparatus illustrated in the drawings is intended for use in processing and applying pressure sensitive adhesives in film form to sheet material, which adhesives .power are demonstrated as a result of rapid cooling only from high temperatures after application, as distinguished from adhesives requiring drying of solvents. Thus, the

2,9ee,oee j apparatus is particularly effective in processing and applying polyvinyl ethyl ethers mixed with a styrene polymer resin or similar solvent-free mixtures of thermoplastic resins, as set forth more particularly in the Sylvester et al. application above referred to. These pressure sensitive adhesives are processed by heating them to a temperature of about 350 F., at which temperature the adhesives still exhibit a viscosity of about forty thousand centipoises. A temperature of 350 is critically close to that at'which discoloration and decomposition begin to occur, so that finely adjusted and reliable heat control at the point of application is required.

The illustrated apparatus provides a vertical cylindrical supply reservoir I'Ohavingat' its upper endan internal counterboard shoulder 12 fitting the mouth of a common form of commercial paper board supply container 14 (Fig. 3). When the supply container is inverted and disposed within the counter-bore above the shoulder 12, the contents of the container are suspended and upon application of heat to the reservoir the adhesive gradually is carried by gravity into the heated bottom of the reservoir which has angularly disposed bottom surfaces 15 declining toward each other. The reservoir has a laterall'y projecting base 16 formed with three parallel passageways 17, 18 and 19 disposed in a horizontal plane and running from the base in parallelism from beneath the reservoir. The central passageway 18 has its rearward end' entering the reservoir at the apex or lower ends of the angularly disposed surfaces 15 to conduct: heated adhesivefrom the reservoir into the passageway. The two outside passageways 17 and 19 are fitted to have inserted therein for. convenient replacement electrical heating cartridges 20 and 22, the cartridges: extending within wedge shaped bottom portions of the reservoir beneath the declining surfaces 15 to provide close fitting support. The rearward end of each cartridge lying beneath a declining surface 15 insures proper heating of the adhesive in the reservoir for drainage into and through the passageway 18.

The rearward endof the adhesive conducting passageway 18, as illustrated in Figs. 1 and 4, is plugged by a capscrew 24. The forward end is pluggedby a valve body 26 having a. slotted enlarged head with a groove 28 into which extends the reduced end of a threaded pin 39 engaging a threaded opening in the base 16, the arrangement being such that the valve 26 maybe rotated to uncover or to close the lower end of an outlet opening 32 running from the adhesive passageway 18 through an upper finished surface 34 on a block 36 forming a part of the laterally projecting base 16. The inner part of the valve 26 is trough shaped with one side open, so that when the open side is alined with the lower end of the outlet opening 32, the adhesive may flow upwardly into the outlet opening.

The upper end of the outlet opening 32 is enlarged to receive and lit an adhesive applying roll 38 secured to the forward end of a shaft 40 rotatably mounted in bearings 42 within a bore of the block. 36, the bearings being arranged horizontally and parallel to the passageways in the projecting base 16.

Cooperating with the adhesive spreading roll 33 is a pressure rollv 44 secured to the forward end of a horizontal shaft 46 rotatable in spaced bearings of a frame 48. The frame 48 is hinged. by a pin 50 to upstanding lugs on the block 36. To enable the pressure roll 44 to be drawn yieldingly' toward the adhesive spreading roll 38', the frame 48' has. a rearwardly extending pin 51 (see Fig. 1) surrounded by a hook on the upper: end of a tension spring 52, the lower end of which similarly surrounds a pin 54: carried by the block 36 directly'beneath thehinge pin. 50. Inthe position of the frame 48 shown in .Fig. 3 thespring 52 draws the roll: 44 downwardly towardlthe roll 38 and consequently if a price ta'gor; other flat article composed. of sheet material 6 (see also Fig. 2) is:- guided between thetrolls it'will. pick up a thinlayeror film 58 of the adhesive. To prevent transfer of thick adhesivefrom the. adhesive applying roll. into. contact with the pressure roll 44 the pressure roll 44 is held raised from the adhesive applying roll a short distance less than the thickness of the tag 56 by an adjusting screw 60 threaded through the frame 48 and extending into engagement with the upper surface 34 of the block 36. The screw 60 is surrounded above the frame 48 by a washer 62 anda. compression spring 64. confined between the washer, which rests on the upper surface of the frame 48 and a handle 66. The arrangement of the spring 52 with the'frame 48l'is s'uchthat. when the frame is rotated about the hinge pin 50 the spring moves across the axis of the hinge pin as the frame approaches a horizontal position and then moves with the frame to the opposite side of the hingepin, holding the frame in position, thus providing convenient access to the pressure applying roll and the parts underlying the frame 48.

To support the price tag 56 during application of the adhesive and angularly bent strip 68 is secured at one end to a vertical surface of the block 36 by a pair of screws 70 (Figs. 1 and 3). A horizontal arm of the strip is beveled and enters between the space between the rolls 38 and 44, so that the price tag enters between thebite of the roll-s in flat condition. To prevent application of adhesive to anything but a limited area of the price tag an edge-gage is provided, consisting of a plate 72 bent at right angles with one arm adjustably secured by screws 74 to the upstanding frame supporting lugs of the block 36.

In the machine of the present invention close and re liable temperature control is afforded and only a limited volume of adhesive issubjected to the maximum temperature at which it is best spread on a price tag by the arrangement of an elongated normally closed circuit thermostat 76 connected in a circuit with the heating cartridges 20 and22 to open their circuit when the temperature reaches a working level. The thermostat is located in a horizontal crosswise relation to the heating cartridges and as close as possible to the juncture of the adhesive passageway 18 with the outlet opening 32. The thermostat also is located similarly in close proximity to the applying roll 38. For this purpose the thermostat extends horizontally through the base block 36 directly above and crossing the-adhesive conducting and heating cartridge passageways within the angle formed between the reservoir and the outlet opening. By this construction the volume of the adhesive subjected to most critical temperature is limited to that contained at the forward part of the adhesive passageway 18 and in the outlet opening 32, which is extremely short. A limited volume only, therefore; is kept heated under closely controlled; high temperature so that the heating cartridges 2t) and 22 may be designed to concentrate the heat at the forward end of the projecting base 16 directly atthe point where the'roll 38 is mounted. The mass and the radiating surfaces, including those of the block 36 are less than those of the reservoir 10 and the rearward portions of the base, so that the reservoir and rearward part of the base 10 are kept cooler than the forward part of the base. Also, it must be appreciated that the reservoir and the rearward portion of the base are cooled on account of the heat required to overcome the latent heat of melting the solid adhesive as it falls from the container 14. The circuit connections for the thermostat 76 will be described more fully hereinafter.

Because of the critically close approach to the temperature at which. discoloration and decomposition of the adhesive begin to occur, it is highly desirable to limit the: volume of adhesive subjected to this temperature to an amount whichwill, in ordinary use of the machine, be applied to a tag and replaced with: fresh adhesive before any appreciable'discoloration. or. decomposition can occur. It is; for. this reason that. the location of. the temperature-control thermostat 76 is chosenat the hottest tuated at 300 F. or slightly above.

point along the path taken by the adhesive from the reservoir to the applying roll 38, the adhesive being spread on the underside of the roll by the approaching column passing through the outlet opening 32 where the greatest fluidity of the adhesive is present. To assist in regulating the temperature at which the thermostat 76 operates an adjusting control is provided consisting of a knob 78 projecting from the left end of the thermostat.

To drive the adhesive spreading roll 38 it is mechanical- 1y connected to an electrical motor 80 provided with a reducing gear 82 having aright angle driven shaft 84, to which is secured a sprocket wheel 86. Surrounding the sprocket wheel 86 is a chain 88 also passing about a second sprocket wheel 90 fixed to the rearward end of the shaft 40. In order that the pressure roll 44 may rotate with the same peripheral speed as the spreading and applying roll 38 the shaft 40 also has secured to it a gear 92 (Fig. 4) meshing with a pinion 94 mounted on the rearward end of the shaft 46 which also carries the pressure roll 44, the gear ratio of the gear 92 and pinion 94 being the same as the ratio of diameters of the applying and pressure rolls. The depths of the teeth on the gear 92 and the pinion 94 are sufficient to enable the spacing between the applying and pressure rolls to be changed for ditferent thicknesses of tags or other sheet materials without disengaging the pinion 94 from the gear 92. When it is necessary to raise the frame 48 for adjustments or other purposes the pinion 94 is lifted from the gear 92 and correspondingly engages the gear 92 when the frame is returned to operative position.

Under some circumstances it is necessary to clean or otherwise dismantle the machine and to facilitate access to the adhesive spreading and applying roll 38 the end of the roll is covered by a plate 96 (Fig. 4) secured to the front face of the block 36 by screws 99 passing through the plate and into threaded engagement with the block. In order to prevent escape of the adhesive from beneath the applying roll 38 when the plate 96 is removed it is necessary to rotate the valve 26 to cover the lower end of the outlet opening 32.

To prevent damage to the driving and reduction gears as well as to the motor 80 the block 36. has passing horizontally through it in parallel relation to the thermostat 76 a second normally open circuit thermostat 98 located further away from the outlet opening of the adhesive passageway than the normally closed circuit thermostat 76. The second, normally open circuit thermostat is connected in circuit with the motor so as to open the motor circuit below a predetermined temperature. Since the location of the second thermostat is further away from the outlet opening it may be adjusted to be actuated at a lower temperature than that existing at the outlet opening. The first thermostat 76 for example, may have an adjustment range such that in the center of the range it is actuated at a temperature of 350 F. At the lower end of its adjustment range it may be ac- Accordingly, .the thermostat 98 is adjusted to be actuated at a temperature of 300 F. or less. In this way there is no possibility of overlapping the adjustment range of the thermostat 76. The thermostat 98 also has an adjusting screw 100 but this adjusting screw is locked out of operation by clamping means consisting of a split block 102 having a threaded opening through which the screw passes and a binding screw 104 passing through the split portions of the block.

a clearance slot between the roll and the block 36 which is closed in part by the plate 96. The thickness of the 'layer of adhesive spread and applied to a price tag by the roll 38 is regulated by a doctor bar 106 engaging 'Tand surrounding a portion of the roll 38 at the right side thereof. The doctor bar 106 is formed with a U-shape and is slidingly mounted for movement toward and from the roll 38 in horizontal grooves 108 formed in the block 36 and in the inner side of the plate'96 (Fig. 5).. The block 36 also is provided with a sight opening 110 through which the doctor bar 106 is visible when the plate 96 is removed (Fig. 3). To adjust the position of the doctor bar toward and from the roll 38, the bar is backed by a pair of adjusting screws 112 threaded in the block 36. The doctor bar cooperates with the roll after receiving a coating of adhesive from the outlet opening 32 to spread a uniform layer of adhesive on the roll for application to the price tag 56, the doctor bar cooperating with the roll at its ascending side. At the descending side of the roll the adhesive is drawn downwardly toward the outlet opening so that there is no possibility of adhesive leakage.

For assembling the parts with a common support the projecting portion of the base 16 has passing upwardly through it into threaded engagement with the block 36 a pair of screws 114 and the base 16 along its under side has a number of threaded openings to receive screws 116, best shown in Fig. 3. The screws 116 pass upwardly from and have their heads countersunk in the lower surface of a heat insulating plate 118. Between the plate 118 and the base 16 the screws 116 carry a set of spacers 120 to enable air to circulate between the heated base 16 and the plate 118. The motor 80 also is secured to the plate 118.

To enable convenient control of the components thusdescribed an electrical circuit is provided, as illustrated in Fig. 6. The circuit is energized by power line conductors 122 and 123. The motor circuit includes the conductor 122, the motor 80, a motor-control switch 124 located in an outlet box 126, a wire 128, running to the thermostat 9-8 and a wire 129 returning to the line conductor 123. To enable an indication to be given when the adhesive is heated to a proper working temperature, an'indicator light 130 is mounted in an outlet box 132 and is connected from the conductor 122 to the wire 128, so that it is illuminated whenever the thermostat 98 closes its contacts.

For controlling the heating cartridges 20 and 22 both are connected to the conductor 122 and to a wire 134 running to one side of the heat-control thermostat 76. The other side of the heat-control thermostat 76 is connected to a wire 136 running to a heat-control switch 138 contained in the outlet box 126. To indicate the times at which the current is flowing through the heating cartridges 20 and 22, the wire 134 has connected to it a second wire 140 running to an indicator light 142 mounted in the outlet box 126. The other side of the indicator light 142 is connected to the line conductor 122 through a wire 144.

Whenever the heat-control switch 138 is closed in order to prepare the machine for operation the signal light 142 is immediately illuminated and the cartridges 20 and 22 begin to heat up the adhesive supply reservoir 10 and the base 16 As soon as the portion of the base 16 surrounding the thermostat 76 reaches an operating temperature, for instance one of 350 F., this thermostat opens the circuit to the heating cartridges and the indicating light 142 is extinguished. Before this occurs, however, the normally open thermostat 98 will close its contacts causing the indicating light 130 to be illurninated. Thus, when the light 142 is extinguished and the light 130 illuminated the operator recognizes that a temperature at which it is possible to start the motor 80 has been reached in the base 16. Accordingly, the switch 124 is closed and the motor is started. If, however, the

switch 124 is closed before the indicator light 130'is illuminated, no harm will be done because the motor circuit also is interrupted by the thermostat 98 until a 'proper temperature is reached at which the I adhesive spread1ng and applying roll 38 is freeto rotate. f

The nature and scope of the invention having been J indicated and a particular embodiment having been described, what is claimed is:

l. Apparatus for applying to sheet material a thin layer of viscous, relatively heat-resistant, pressure-sensitive adhesive, such as a substantially solvent-free mixture of thermoplastic resins, the viscosity of which is about forty thousand centipoises at a critical temperature of 350 R, said apparatus having a supply reservoir formed with a laterally extending base provided with parallel passageways running horizontally beneath the reservoir in the base, the rearward end of one of which passageways enters the reservoir and conducts adhesive into the base from said reservoir and an electrical heating cartridge fitted in another of the passageways, an upper surface of the base having an outlet opening running from the forward end of the adhesive passageway, in combination with an elongated thermostat connected with. the heating cartridge for regulating the temperature of the adhesive as it passes through the outlet opening in the base, said thermostat extending horizontally through the base directly above and crossing the adhesive conducting and heating cartridge passageways at the juncture of the adhesive passageway and the outlet opening.

2. Apparatus for applying to sheet material a thin layer of viscous, relatively heat-resistant, pressure-sensitive adhesive, such as a substantially solvent-free mixture of thermoplastic resins, the viscosity of which is about forty thousand centipoises at a critical temperature of 350 F., said apparatus having a supply reservoir formed with a laterally extending base provided with parallel passageways running horizontally beneath the reservoir in" the base, the rearward end of one of which passageways enters the reservoir and conduits adhesive into the base from said reservoir and an electrical heating cartridge fitted in another of the passageways, an upper surface of the base having an outlet opening running from the forward end of the adhesive passageway, in combination with an elongated thermostat connected with the heating cartridge for regulating the temperature of the adhesive as it passes through the outlet opening in the base, said thermostat extending horizontally through the base directly. above and crossing the adhesive conducting and heating cartridge passageways at the juncture of the adhesive passageway and the outlet opening, and a second elongated heating cartridge in another of the passageways at the opposite side of the adhesive passageway from the first-mentioned heating cartridge.

3. Apparatus for applying to sheet material a thin layer of viscous, relatively heat-resistant, pressure-sensitive adhesive, such as a substantially solvent-free mixture of thermoplastic resins, the viscosity of which is about forty thousand centipoises at a critical temperature of 350 F., said apparatus having a supply reservoir formed with a laterally extending base provided with parallel passageways running horizontally beneath the reservoir in the base, the rearward end of one of which. passageways enters the reservoir and conducts adhesive into the base from said reservoir and an electrical heating cartridge fitted in another of the passageways, an upper surface of the base having an outlet opening running from the forward end of the adhesive passageway, in combination with an elongated thermostat connected with the heating cartridge for regulating the temperature of the adhesive as it passes through the outlet opening in the base, said thermostat extending horizontally through the base directly above and crossing the adhesive conducting and heating cartridge passageways at the juncture of the adhesive passageway and the outlet opening, a second elongated heating cartridge in another of the passageways at the opposite side of the adhesive passageway" from the first-mentioned heating cartridge, and an adhesive spreading roll in the outlet opening of, the base, an electrical motor mechanically connected for driving the spreading roll, and a, second elongated thermostat arranged in horizontal parallel relation to the first-men- 5 tioned thermostat but further away from the outlet opening in the adhesive passageway and electrically connected in circuit with the motor to open the motor circuit whenever the temperature of the base drops below the critical temperature of the adhesive.

4. Apparatus for applying to sheet material a thin layer of viscous, relatively heat-resistant, pressure-sensitive adhesive, such as a substantially solvent-free mixture of thermoplastic resins, the viscosity of which is about forty thousand centipoises at a critical temperature of 350 F., said apparatus having a supply reservoir formed with a laterally extending base provided with parallel passageways running horizontally beneath the reservoir in the base, the rearward end of one of which passageways enters the reservoir and conducts adhesive into the base from said reservoir and an electrical heating cartridge fitted in another of the passageways, an upper surface of the base having an outlet opening running from the forward end of the adhesive passageway, in combination with an elongated thermostat connected with the heating cartridge for regulating the temperature of the adhesive as it passes through the outlet opening in the base, said thermostat extending horizontally through the base directly above and crossing the adhesive conducting and heating cartridge passageways at the juncture of the adhesive passageway and the outlet opening, a second elongated heating cartridge in another of the passageways at the opposite side of the adhesive passageway from the first-mentioned heating cartridge, and an adhesive spreading roll in the outlet opening of the base, an electrical motor mechanically connected for driving the spreading roll, and a second elongated thermostat arranged in horizontal parallel relation to the first-mentioned thermostat but further away from the outlet opening in the adhesive passageway and electrically connected in circuit with the motor to open the motor circuit whenever the temperature of the base drops below the critical temperature of the adhesive, the first-mentioned thermostat being provided with a hand adjusting control for regulating the response through a range of temperatures and the second-mentioned thermostat being provided with adjusting means and means for locking the adjusting means for the second-mentioned thermostat to prevent its actuation at a temperature above that at which he first thermostat is actuated.

5. Apparatus for applying to sheet material a thin layer of viscous relatively heat-resistant, pressure-sensitive adhesive, such as a substantially solvent-free mixture of thermoplastic resins, the viscosity of which is about forty thousand centipoises at a critical temperature of 350 F., said apparatus having a heated supply reservoir formed with a laterally extending base provided with parallel passageways extending horizontally beneath the reservoir in the base, one of which passageways enters the reservoir and conducts heated adhesive into the base from said reservoir, and another of which passageways is fitted with an electrical heatingcartridge, the upper surface of the base having an outlet opening from one end of the adhesive passageway, an adhesive spreading roll in the outlet opening of the base, a shaft to which the roll is secured rotating about a horizontal axis extending parallel to the passageways in the. base, an: electrical motor mechanically connected to the roll shaft, in combination with an elongated thermostat extending horizontally through the base at right angles to the adhesive and heating cartridge passageways between theroll shaft and said passageways, said thermostat being, connected in circuit with the heating cartridge to control the temperature of the adhesive in the adhesive passageway.

6. Apparatus for applying to sheet material a thin layer of viscous, relatively heat-resistant, pressure-sensitive adhesive, such as asubstantially solvent-free mixture. of. thermoplastic resin, the viscosity of which is about-forty thousand centipoises at a critical temperature of 350 F., said apparatus having a supply reservoir fromed with a laterally extending base provided with parallel passageways running horizontally beneath the reservoir in the base, the bottom of the reservoir having angularly disposed surfaces declining toward each other to form wedge-shaped bottom portions beneath the declining surfaces and above the parallel passageways, one of which passageways enters the reservoir at the apex of the angularly disposed surfaces and conducts heated adhesive into the base from said reservoir, said adhesive conducting passageway having an outlet opening in the projecting portion of the base, and means for spreading and applying a layer of adhesive to sheet material at the end of the outlet opening, in combination with means for heating the reservoir and base comprising an electrical heating cartridge disposed in another of said passageways and arranged to be supported at its rearward end within a wedge-shaped bottom portion of the reservoir.

7. Apparatus for applying to sheet material a thin layer of viscous, relatively heat-resistant, pressure-sensitive adhesive, such as a substantially solvent-free mixture of thermoplastic resins, the viscosity of which is about forty thousand centipoises at a critical temperature of 350 F., said apparatus having a supply reservoir formed with a laterally extending base, the bottom of which has an angularly disposed surface declining from one side to form a wedge-shaped bottom portion beneath the declining surface, in combination with parallel passageways running in a horizontal plane beneath the reservoir into the base, one of which passageways enters the reservoir at the lower end of the angularly disposed surface to conduct heated adhesive from the reservoir into the passageway and heating means in another of said passageways extending into the wedge-shaped bottom portion of the reservoir.

8. Apparatus for applying to sheet material a thin layer of viscous relatively heat-resistant, pressure-sensitive adhesive such as a substantially solvent-free mixture of thermoplastic resins, the viscosity of which is about forty thousand centipoises at a critical temperature of 350 F., said apparatus having a supply reservoir formed with a laterally extending base, the bottom of which has angularly disposed surfaces declining toward each other to form two wedge-shaped bottom portions beneath the declining surfaces, in combination with three parallel passageways running in a horizontal plane beneath the reservoir into the base, the central one of which passageways enters the reservoir at the apex of the angularly disposed surfaces to conduct heated adhesive from the reservoir into the central passageway, and the two outer passageways extending into the wedge-shaped bottom portions of the base beneath the declining bottom surfaces of the reservoir.

9. Apparatus for applying to sheet material a thin layer of viscous, relatively heat-resistant, pressure-sensitive adhesive, such as a substantially solvent-free mixture of thermoplastic resin, the viscosity of which is about forty thousand centipoises at a critical temperature of 350 B, said apparatus having a supply reservoir formed with a laterally extending base provided with parallel passageways running horizontally beneath the reservoir in the base, the bottom of the reservoir having angularly disposed surfaces declining toward each other to form wedge-shaped bottom portions beneath the declining surfaces and above the parallel passageways, one of which passageways enters the reservoir at the apex of the angularly disposed surfaces and conducts heated adhesive into the base from said reservoir, said adhesive conducting passageway having an outlet opening in the projecting portion of the base, and means for spreading and applying a layer of adhesive to sheet material at the end of the outlet opening, in combination with means for heating the reservoir and base comprising two electrical heating cartridges disposed in others of said passageways at opposite sides of the adhesive conducting passageway and arranged to be supported at their rearward ends within the wedge-shaped bottom portions of the base.

10. Apparatus for applying to sheet material a thin layer of viscous, relatively heat-resistant, pressure-sensitive adhesive, such as a substantially solvent-free mixture of thermoplastic resin, the viscosity of which is about forty thousand centipoises at a critical temperature of about 350 F., said apparatus having a supply reservoir formed with a laterally extending base provided with parallel passageways running horizontally beneath the reservoir in the base, the rearward end of one of which passageways enters the reservoir and conducts heated adhesive into the base from said reservoir and an electrical heating cartridge fitted in another of the passageways, and an upper surface of the base having an outlet opening connecting the forward end of the adhesive conducting passageway, in combination with an elongated normally closed circuit thermostat connected in circuit with the heating cartridge for regulating the temperature of the adhesive as it passes through the outlet opening in the base, said normally closed thermostat extending horizontally through the base directly above and crossing the adhesive conducting and heating cartridge passageways at the juncture of the adhesive passageway and at the outlet opening, an adhesive spreading roll in the outlet opening of the base, an electrical motor mechanically connected for driving the spreading roll, and a second elongated normally open circuit thermostat electrically connected to the driving motor and arranged in horizontal parallel relation to the first-mentioned thermostat but farther away from the outlet opening in the adhesive passageway to open the motor circuit whenever the temperature of the base drops below the critical temperature of the adhesive.

References Cited in the file of this patent UNITED STATES PATENTS 1,391,281 Snyder Sept. 20, 1921 2,144,263 Lane Jan. 17, 1939 2,192,453 Rentsch Mar. 5, 1940 2,263,569 Campbell Nov. 25, 1941 2,710,590 Gerard June 14, 1955 2,772,653 Williamson et a1. Dec. 4, 1956 2,787,241 Kelley Apr. 2, 1957 2,878,777 Paulsen Mar. 24, 1959 

